Synthesis of 1, 1-difluorinated hydrocarbons



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I as I SSIS OF 1,1-DIFLUORINATED HYDROCARBONS Paul Tarrant and Marvin R. Lilyquist, Alachua County,

Fla., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Application August 17, 1954, Serial No. 450,565

18 Claims. (Cl. 260-653) This invention relates to the synthesis of 1,1-difiuorinated hydrocarbons, and more particularly to the synthesis of 1,1-difluorinated dienes and homologs thereof from tates P ment- 2,749,378 Patented June 5, 1956 We have found that the desired replacement of two chlorine atoms in the 1-position of the starting material of the type formula C13CHY .CY Br.CHzCl (wherein Y and Y have the meanings above indicated) can be effected with high yields by reacting it with a fluoro compound of antimony, preferably with a mixture of two different fluoro compounds of antimony, sc. antimony trifluoride and antimony trifluorodichloride, which results in the formation of a first, saturated, intermediate compound of the general type formula Removal of 1 mol of BrCl from this first intermediate 15 compound, e. g., by reaction with powdered zinc, results 1,1,1,4-tetrachloro-3-br0mob11tane r certaln hornologs in the formation of a second intermediate compound, thereof), and to the productionof several 1,1-d1fluor1- a ppdiiiuorinated alkene f the type f l nated 1ntermed1ate compounds in the course of such synthesis. CIF2C.CHY .CY :CH2

The 1,1-difluorinated dienes which may be synthesized in accordance with the process herein claimed, are repre- This second intermediate compound iS then converted sented by the general formula F2CZCY .CY :CHz by dehydrochlorination, i. e., removal of 1 mol of HCl, wherein Y and Y are either hydrogen or methyl; repree. g, by refluxing with a base, e. g., potassium hydroxide, sentative dienes falling under this general formula are into the 1,1-difluorinated diene of the type formula 1,1 difluorobutadiene 1,3, 1,1 difiuoro-Z-methyl-buta- F2C:CY .CY :CH2. diene-1,3 and l,1-difluoro-3-methyl-butadiene-l,3, which The starting material 1,l,1,4-tetrachloro-3-bromocompounds are disclosed and claimed in copending apbutane may be readily obtained by reacting bromotriplication Serial No. 355,848, Paul Tarrant and Alan M. chloromethane with allyl chloride as set forth, for in- Lovelace, filed May 18, 1953, assigned to the Governstance, in Kharasch Patent No. 2,468,208, and we lay ment of the United States as represented by the Secretary no claim to this particular reaction. Its 2- and 3-methyl of the Army. The starting materials are represented substituted homologs can be synthesized by analogous by the general formula Cl3C.CHY .CY Br.CH2Cl wherereactions, for which see also Kharasch Patent No. in Y and Y are either hydrogen or methyl; representa 2,574,832. tive starting compounds are 1,1,1,4-tetrachloro-3-bromo- After a series of experiments we have found that high butane, 1,1,1,4-tetrachloro-2-methyl-3brornobutane, and yields, of the order of 51%, of the saturated 1,1-difluoro l,1,1,4-tetrachloro-3-methyl-3-bromobutane. intermediate compound are obtained by reacting the The conversion of the saturated unfiuorinated starting starting compound, e. g., 1.,1,1,4-tetrachlorobromobutane compounds to the 1,1-difiuorinated dienes takes place, by reaction with a fluoro compound of antimony, e. g., in accordance with the present invention, by replacing with a mixture of antimony tritiuoride and antimony tritwo chlorine atoms on the l-carbon of the starting ma- 4o flnorodichloride. This first intermediate compound is terial with two fluorine atoms, and converting the interthen de-hydrobromochlorinated to form the desired 1,1- mediate product by dehydrobromochlorination (i. e. by difluorinated diene in accordance with the type reactions removal of 1 mol of BrCl and 1 mol of HCl) to the outlined above, which type reactions will be illustrated 1,1-difiuoro diene; We prefer to carry out the dehydroby specific examples in the following portion of our bromochlorination reaction in two stages, preferably by specification. The yield of the first intermediate comfirst removing 1 mol of BrCl to form a 1-chloro-1,1- pound is materially affected by the concentration of the difluoro alkene, and then removing 1 mol of HCl for fluoro antimony compounds in terms of the starting metthe formation of the end product 1,1-difluorinated diene. terial; thus, a 51% yield was achieved with a concen- In the case of conversion of 1,1,1,4-tetrach1oro-3-bromotration of a mixture of 1.7 mols of antimony trifluoride butane to 1,l-difluoro-butadiene-l,3, this may be repreand 1.3 mols antimony trifluorodichloride, While at a sented by the following type reacti n: concentration of .6 mols and .4 mols of the same anti- 2F 1 mony fluoro compounds the yield was only 17%. CI'C'CHK-GHBTCHQCI Bro1 The physical constants of typical intermediate and C1F2C.CH2.CHBI.CH2C1 final products herein mentioned are set forth in the fol- CiF2C.CH2.CHZCHfl CF22CH.CH:CH2 55 lowing table:

TABLE MR1) Compound 6 'h g an d4 Galcd. Found 1 1 -difluoro-1,4-dichloro-3-bromobutane CFzClGHzCHBrCHzOL- 52.4 10 25 1.4551 1. 731 37.97 37.93 1 1-chloro-1,l-difiuoro-butene-3 CFa CICH1CH=CH2 49.2 760 25 1.3550 1.103 24. 88 24.88

1, l-difluoro-butadiene-l, 3OF2= GECH=CH2 3.54.0 760 1 1 -di.fluor0 -2-methyl-butadiene-1,

3CF1:OCHs.CH:CH2 39.0 760 25 1,3755 0.9582 24.35 25.1 1 1, 1 -difiuoro-3 -methyl-butadiene-1,

3CF2ZUH.OGH3ZOH2 35.5 760 25 1, 3705 0.9463 24.35 24.875

1 Silver equivalent=mol calculated 80.3, found 0 Chlorine: calculated 25.0%, found 28.3%.

Example la FLUORINATION OF 3-BROMO-l,1,lA-TETRACHLORO- BUIANE Powdered antimony trifluoride (3 mols) was placed in a flask equipped with stirrer and reflux condenser. A stream of chlorine was introduced near the bottom of the flask until 90 grams (1.3 mols) had been absorbed. The flask was then carefully cooled in an ice bath to give a thin film of SbF3.SbF3Cl2 which could be broken up and dispersed throughout the organic compound to be fluorinated. After the addition of CClsCHzCHBrCHzCl (550 g., 2 mols) vigorous stirring was begun and the mixture allowed to warm to 40-50 where it was maintained for three hours.

The reaction mixture was made slightly basic with potassium carbonate and steam distilled to give 356 g. of organic product. Fractionation through a 40 cm. column packed with protruded packing gave a forerun of 16.5 g. of CFzClCi-IzCl-IFCHaCl, B. P. 38-50/27 mrn, a main fraction of 274 g. (51% yield) of l,1-difluoro-1,4-dichloro-S-bromobutane (CFaClCHzCl-lBrCHzCl), B. P. 52-57/11 mm., and a final fraction of 32 g. (6.2% conversion) of CFClzCHzCHBrCHzCl, B. P. 7'l.4/ 10 mm., 21 1.4916, (I4 1.784, MRD calcd. 42.9, found 41.8, silver eq. calcd. 64.6, found 65.1.

Example 1b Example Ia was repeated, with reduced amounts of I antimony fluoride (1 mol) and chlorine (.6 mol); reaction temperature with CClaCI-IzCI-IBrCHzCl was 62 C. 17% yield of CFzClCl-IzCHBrCI-IzCl was obtained.

Example II FORMATION OF LCHLORO-l,l-DIFLUOROBUTENE-3 0.93 mol of CFzClCHzCHBrCl-IzCl was added to a vigorously stirred slurry of zinc dust (1.54 mols) and isopropanol (110 ml.) maintained at refluxing temperature. After 3 hours refluxing, the mixture was steam distilled and the water insoluble layer separated, dried and fractionated to give a 79% yield of l-chloro-l,l-difluorobutone-3 (CFzClCHzCH CHz), B. P. 49.2.

Example HI FORMATION OF 1,1 DIFLUOROBUTADIENE-L3 A solution of 2.68 mols of potassium hydroxide in 450 g. of ethanol was slowly added to 1.66 mols of CFzClCHaCH CHz Example IV Example In was repeated with 2 mols of l,1,1,4-tetrachloro-2methyl-3-bromobutane as the starting material, and the first l,l-difluorinated, saturated, intermediate compound thus obtained was converted to 1,1-difluoro-2- methyl-butadiene-1,3 (B. P. 39 C.) by dehydrobromochlorination through the successive reactions of Examples II and III.

Example V 1,1-difluoro-3-methyl-butadiene-1,3 (B. P. 35.5 C.) was obtained by following the procedure of Example IV, but using 2 mols of l,l,1,4-tetrachloro-3-methyl-3-bromobutane as starting material.

We have also found that the 1,1,4-trichloro-1-fluoro-3- bromobutane (CFClaCHaCHBnCI-lzCl) obtained as the final fraction of Example Ia can be converted to l-chloro- 1-fluoro-butadiene-l,3 by a dehydrobromochlorination reaction analogous to Examples III and IV. l-chloro-lfluoro-butadiene polymerizes on standing in the open to a vulcanizable elastomer. The following example describes a preferred way of accomplishing this dehydrobromochlorination reaction in two steps.

Example Vla DEBROMOCHLORINATION OF 1,1,4-TRICHLORO-1- FLUORO-3-BROMOBUTANE 1 mol of CFClzCHzCHBnCHzCl obtained as the final fraction in Example In was added to a vigorously stirred slurry of zinc dust (1.3 mols) in methanol (380 ml.) maintained at the reflux temperature. The reaction was carried out in three hours. The mixture was steam distilled and the water insoluble layer separated, dried and fractionated to give 58 g. of l,1-dichloro-1-fluoro-butene- 3 (CFClzCHz.CH:Cl-lz), B. P. 88 at 760 mm. Hg; 11 1.4104; d4 1.188; MRD calcd. 39.85, found 30.00; chlorine calcd. 49.6%, found 49.6%.

Example Vi'b FORMATION OF l-CHLOROl-FLUORO-BUTADIENE To a refluxing solution of 0.4 mol of 1,1-dichloro-lfluorobutene-3 (obtained according to Example Vla) in ethanol was added dropwise a solution of potassium hydroxide (0.63 mol) in ml. of ethanol. The addition was carried out over a period of one and a half hours and the mixture was refluxed an additional hour. The product was washed with water, dried and distilled to give 23 g. (53.5% yield) of l-chloro-lfluorobutadiene-1,3 (CFCI:CH.CH:CH2), B. P. 53.4 C. at 760 mm. Hg; 11 1.4267; Z4 1.066; MRn calcd. 24.51, found 25.50.

The respective intermediate compounds 1-chloro-1,ldifluorobutene-3 (Example H) and 1,1-dichloro-1-fluorobutene-3 (Example Vla) may be expressed by the general formula HalClFCCI-IZCI-LCHZ, wherein Hal is F or Cl.

From the foregoing description of our invention it will be apparent to those skilled in the art that 1',1-difluorinated dienes can be obtained from 1,1,l,4-tetrachloro-3-bromobutane and its homologs, by convering two chlorine atoms in the l-position of the starting material into fluorine atoms, and dehydrobromochlorinating the intermediate saturated compound thus formed. The resulting end products are polymerized and vulcanizable to form elastomers having valuable industrial properties more fully set forth in eopending application Serial No. 355,848. We do not wish to be understood to limit the scope of our invention to the examples specifically herein set forth, inasmuch as modifications and adaptations within the spirit of our invention will readily occur to those skilled in the art. We thus intend to claim our invention broadly and to define its scope by the appended claims.

We claim:

1. The process of converting a compound having the general formula Cl3C.CHY.CBrY-.C.-sCl wherein Y and Y are members of the group consisting of hydrogen and methyl, into a compound having the general formula FXC:CY .CY :CH2 wherein X is a member of the group consisting of chlorine and fluorine and wherein Y and Y have the same meanings as aforesaid, comprising reacting said first-named compound with a fluoro compound of antimony, whereby an intermediate compound is obtained, wherein X, Y and Y have the same meanings as aforesaid, and debromochlorinating and dehydrochlorinating said intermediate compound.

2. The process of converting a compound having the general formula C13C.CHY .CBrY .CH2Cl wherein Y and Y are members of the group consisting of hydrogen and methyl, into a compound having the general formula F2C:CY .CY :CH2 wherein Y and Y have the same meanings as aforesaid, comprising reacting said firstnamed compound with a fluoro compound of antimony, and debromochlorinating and dehydrochlorinating the intermediate 1,1-difluorinated compound thus obtained.

3. The process of converting 1,1,1,4-tetrachloro-3- bromo-butane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrachloro-3-bromo-butane with a fluoro compound of antimony, and debromochlorinating and dehydrochlorinating the intermediate 1,1-difluorinated compound thus obtained.

4. The process of converting 1,l,lA-tetrachloro-Z-methyl-3-bromo-butane into l,1-difluoro-2-methyl-butadiene, comprising reacting said 1,1,1,4-tetrachloro-2-methyl-3- bromo-butane with a fluoro compound of antimony, and debromochlorinating and dehydrochlorinating the intermediate l,l-difluorinated compound thus obtained.

5. The process of converting 1,1,1,4-tetrachloro-3- methyl 3 bromo butane into 1,1 difluoro 3-methylbutadiene, comprising reacting said 1,l,1,4-tetrachloro-3- methyl-3-bromo-butane with a fluoro compound of antimony, and debromochlorinating and dehydrochlorinating ing the intermediate 1,1-difluorinated compound thus obtained.

6. The process of converting a compound having the general formula C13C.CHY .CBrY .CH2Cl wherein Y and Y are members of the group consisting of hydrogen and methyl, into a compound having the general formula F2C:CY .CY :CH2 wherein Y and Y have the same meanings as aforesaid, comprising reacting said firstnamed compound with a mixture of antimony trifluoride and antimony trifluorodichloride, and debromochlorinating and dehydrochlorinating the intermediate 1,1-difluorinated compound thus obtained.

7. The process of converting 1,l,1,4-tetrachloro-3- bromo-butane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrachloro-3-bromo-butane with a mixture of antimony trifluoride and antimony trifluorodichloride, and debromochlorinating and dehydrochlorinating the intermediate 1,1-difluorinated compound thus obtained.

8. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrach1oro-3-bromobutane with a fluoro compound of antimony, and debromochlorinating and dehydrochlorinating the intermediate compound 1,1- difluoro-1,4-dichloro-3-bromobutane thus obtained.

9. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrachloro-3-bromobutane with a fluoro compound of antimony, debromochlorinating the intermediate compound 1,l-difiuoro-l,4-dichloro-3-bromobutane thus obtained, and dehydrochlorinating the 1- chloro-l,1-difluoro-butene-3 obtained by said last named reaction.

10. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrachloro-3-bromobutane with a mixture of antimony trifluoride and antimony trifluorodichloride, debromochlorinating the intermediate compound thus obtained, and dehydrochlorinating the 1- chloro-1,1-difluoro-butene-3 thus obtained.

11. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising reacting said 1,1,1,4-tetrachloro-3-bromobutane with a mixture of antimony trifluoride and antimony trifluorodichloride, reacting the intermediate compound thus obtained with zinc, and reacting the 1-chloro-1,l-difiuorobutene-3 thus obtained with potassium hydroxide.

12. The process of converting a compound having the general formula Cl3C.CHY .CY Br.CHzCl wherein Y and Y are members of the group consisting of hydrogen and methyl, into a compound having the general formula F2C:CY .CY :CH2, wherein Y and Y have the same meanings as aforesaid, comprising replacing two chlorine atoms in the 1,1 position of said first-named compound by two fluorine atoms, whereby an intermediate compound having the general formula wherein Y and Y have the same meanings as aforesaid, is obtained, and debromochlorinating and dehydrochlorinating said intermediate compound.

13. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising replacing two chlorine atoms in the 1,1 position of 1,1,1,4- tetrachloro-3-bromobutane by two fluorine atoms, debromochlorinating the intermediate compound 1,1-difluorol,4-dichloro-3-bromobutane thus obtained, and dehydrochlorinating the l-chloro-l,1-difluoro-butene-3 obtained by said last-named reaction.

14. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1,1-difluoro-butadiene, comprising replacing two chlorine atoms in the 1,1 position of said first-named compound by two fluorine atoms, and debromochlorinating and dehydrochlorinating the intermediate compound 1,l-difluoro-1,4-dichloro-3-bromobutane thus obtained.

15. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1-chloro-l-fiuorobutadiene, comprising reacting said first-named compound with a fluoro compound of antimony, separating 1,1,4-trichloro-1- fluoro-3-bromobutane from the reaction product, and debromochlorinating and dehydrochlorinating said lastnamed compound to form 1-chloro-1-fluoro-butadiene.

16. The process of converting 1,1,1,4-tetrachloro-3- bromobutane into 1-chloro-1-fluorobutadiene, comprising reacting said first-named compound with a fluoro compound of antimony, separating 1,1,4-trichloro-1- fluoro-3-brom0butane from the reaction product, debromochlorinating said 1,1,4-trichloro-1-fluoro-3-bromobutane to form 1,l-dichloro-1-fluorobutene-3, and dehydrochlorinating said 1,l-dichloro-l-flu0ro-butene-3 to form l-ohloro-l-fluorobutadiene.

17. l-chloro-l-fluoro-butadiene.

18. Avulcanizable elastomeric polymer of 1-chloro-1- fluoro-butadiene.

References Cited in the file of this patent UNITED STATES PATENTS 2,647,110 Wiseman July 28, 1953 2,686,207 Crane et a1 Aug. 10, 1954 OTHER REFERENCES Wakefield: Abstracts of Papers, India Rubber World, vol. 123, pages 581-2 (February 1951). 

1. THE PROCESS OF CONVERTING A COMOUND HAVING THE GENERAL FORMULA CL3C.CHY1.CBRY2.CH2CL WHEREIN Y1 AND Y2 ARE MEMBERS OF THE GROUP CONSISTING OF HYDROGEN AND METHYL, INTO A COMPOUND HAVING THE GENERAL FORMULA FXC:CY1.CY2:CH2 WHEREIN X IS A MEMBER OF THE GROUP CONSISTING OF CHLORINE AND FLUORINE AND WHEREIN Y1 AND Y2 HAVE THE SAME MEANINGS AS AFORESAID, COMPRISING REACTING SAID FIRST-NAMED COMPOUND WITH A FLUORO COMPOUND OF ANTIMONY, WHEREBY AN INTERMEDIATE COMPOUND
 18. A VULCANIZABLE ELASTOMERIC POLYMER OF 1-CHLORO-1FLUORO-BUTADIENE. 